P4C800-E Northbridge - Too Hot to Touch (Random Reboots)

Discussion in 'Asus' started by Greg Wilder, Jul 14, 2004.

  1. Greg Wilder

    Greg Wilder Guest

    I have a homebuilt P4C800-E PC, with a 3.2GHZ P4. Not doing any

    Worked fine for about 4-5 months, then started getting random reboots
    and BSOD. Have unistalled, upgraded, new ram, etc.

    My CPU temp is running around 49c. However, my Northbridge heatsink is
    too hot to touch. Do you think I have a problem with the MB, or should
    I look at an active cooler for the Northbridge.

    Greg Wilder, Jul 14, 2004
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  2. Greg Wilder

    Paul Guest

    If you look up the power dissipation specs for the Northbridge, the
    family runs in the 12W range. Temperature can depend on how aggressive
    the memory components are, that you are using (i.e. DDR500 will make
    it warmer). When you bump up the Vdimm for your memory, that also
    bumps the 2.5-2.6V that feeds the Northbridge, which makes it hotter.

    I suspect, however, that some supply tied to that chip is way out of
    wack. It may not be a voltage which registers in the hardware monitor
    (a shortcoming I don't appreciate - all supplies should show up in the
    monitor, as all it would take is an analog mux to add them). Take a
    look in the hardware monitor anyway, to see if anything there looks
    out of line.

    I would RMA the board, before it destroys some of your other hardware,
    like your DDR memory for example.

    My rule of "thumb" is, if you cannot hold a finger on a heatsink
    for more than 2 seconds, it is running at 50-55C. By your description,
    yours is a lot hotter than that.

    Here are the absolute max voltage values for the 875P Northbridge:

    Absolute Maximum Ratings
    Symbol Parameter Min Max Unit
    VCC 1.5 V Core Supply -0.3 to 1.75 V
    VCC_AGP 1.5 V AGP Supply -0.3 to 1.75 V
    VCCA_AGP 1.5 V Analog AGP Supply -0.3 to 1.75 V
    VCC_HI 1.5 V HI/CSA Supply -0.3 to 1.75 V
    VTT VTT Supply -0.3 to 1.75 V
    VCC_DDR 2.6 V DDR System Memory Interface Supply -0.5 to 3 V
    VCCA_DDR 1.5 V Analog Supply for System Memory PLLs -0.3 to 1.75 V
    VCC_33 3.3 V Supply -0.3 to 3.6 V
    VCCA_FSB 1.5 V Host PLL Analog Supply -0.3 to 1.75 V

    Based on that list, I would expect to see a 1.5V supply perhaps tied
    to the same supply as the AGP I/O, a 2.6V Vdimm supply shared by
    Northbridge and DIMMs, and a 3.3V supply (could come straight from the
    PSU). VTT is also a separate supply. So, if any of those is
    radically wrong, or if the clock frequency being fed to the
    Northbridge is wrong, that will make the chip hot.

    It doesn't take a lot of air movement through the Northbridge
    heatsink, to cool it down. I worked on a 865G board last year
    that had a heatsink running at over 75C. That is because the
    heatsink got zero air flow. (It was in a weird low profile
    enclosure.) Adding a 40mm fan to the top of the heatsink
    brought it down to 37C, as measured by a portable
    digital thermometer. Again, if you find that blowing a little
    air over it, is not bringing it into the "touchable"
    temperature zone, there must be something seriously wrong.
    Amazingly, there wasn't a hint of instability on that board,
    even though the silicon die was probably running at 100C.
    That means your Northbridge is probably hotter than that.

    To measure any of the voltages above, you would probably have
    to flip the board up on edge, and access connections on the
    back of the board. This is not too practical for hobbyist
    purposes - you would need a clamp or something, to hold it
    vertical while you work on it.

    Another test you might want to try, is feel all the MOSFETs.
    These are the devices with the three leads coming out of them,
    of which there are a large number on the board. I expect you
    are going to find some of those are hot as well. Knowing
    which one or one(s) are hot, can help narrow down which supply
    voltage has gone nuts. (I have a P4C800-E, and no, I haven't
    figured out what all the MOSFETs do...) A poster yesterday,
    reported hot MOSFETs on another member of that family of boards,
    so you might see something similar. MOSFETs soldered to the board,
    are only good for one or two watts of power dissipation, before
    they get good and hot. That is one reason I'm not too happy to
    see Asus using them as part of linear regulators - they are fine
    until something on the board starts drawing a bit too much current.

    Paul, Jul 14, 2004
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  3. Greg Wilder

    Greg Wilder Guest

    Yes, it is too hot to touch via my finger for more than a couple of
    seconds. Took the case off to see if that helps. Also, used a can of
    compressed air upside down to cool it temporarily. Has been up 24hrs
    now, but sometimes it will go 2-3 days, then crash 3-4 times in one

    I did have the RAM voltage up to about 2.65 - 2.75 to see if that was
    the instability issue, so that may have caused a temperature problem.

    I will probably swap out the MB just to make sure.

    By the way, this is the error I am getting. Windows online support
    indicates a driver issue. However, I have updated everything, and
    removed the latest SW I installed right before the problem started.

    Error code 1000008e, parameter1 c0000005, parameter2 bf851b3c,
    parameter3 b7b289e0, parameter4 00000000.

    I am using Mushkin memory, so I may swap that too.
    Thanks to all
    Greg Wilder, Jul 14, 2004
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